This invention relates to direct-fired fuel gas heating or heat treating furnaces such as for annealing steel strip and especially to a burner adapted for mounting in the furnace wall for mixing and igniting fuel gas and air and for producing a swirl effect in the combustion zone that results in a flat-flame pattern. More particularly, the invention relates to direct-fired fuel gas burner construction that produces a generally flat-flame to generate a large expanse of heat radiation.
Flat-flame burners of the general type to which the present invention is directed are adapted to impart a swirling movement to a mixture of fuel, gas and air so that when ejected from the nozzle, the mixture and flame flares outwardly. As a result, the swirling gaseous mixture progresses from the nozzle at a relatively low forward velocity but with a relatively larger tangential velocity. Thus, the flame spreads outwardly in radial fashion and tends to remain close to the surface of the combustion block.
The result of the general construction described above is a wide, flat expanse of flame with sufficient turbulence for intimate mixing of fuel, gas and air and complete combustion. The combustion takes place largely in a radially extending path rather than in an axial path so that the flame extends over a wide area.